Joint resource map design of dm-rs and pt-rs

ABSTRACT

A method, network node and wireless device in a wireless communication system for one of transmitting and receiving a phase-tracking reference signal, PT-RS. The method includes obtaining information about a position in a time domain of a scheduled first demodulation reference signal, DM-RS, in a slot, and one of transmitting and receiving the PT-RS within the slot, the position of the PT-RS depending on the position in the time domain of the scheduled first DM-RS.

TECHNICAL FIELD

This disclosure relates to wireless communications, and in particular toa method, network node and wireless device for scheduling phase trackingreference signals, PT-RS, jointly with demodulation reference signals,DM-RS.

BACKGROUND

The physical layer of New Radio (NR) (the third generation partnershipproject (3GPP) fifth generation (5G) mobile radio systems) is expectedto handle a vast number of different transmission scenarios by operatingin the frequency range from below 1 GHz to 100 GHz. Carrier frequenciesabove 6 GHz are not supported by long term evolution (LTE), so NRrequires a new and flexible design for the physical layer which offersgood performance in a wider range of frequencies than the physical layerof LTE.

Similar to LTE, NR will use orthogonal frequency division multiplexing(OFDM) based waveforms with reference signals and physical layerchannels mapped on a time-frequency resource grid. NR has an ultra-leandesign that minimizes always-on transmissions to enhance network energyefficiency and ensure forward compatibility. In contrast to the setup inLTE, the reference signals in NR are transmitted only when necessary.Demodulation reference signals (DM-RS) and phase-tracking referencesignals (PT-RS) are two variations of reference signals among theothers.

DM-RS is used to estimate the radio channel for demodulation. DM-RS iswireless device-specific, can be beamformed, confined in a scheduledresource, and transmitted only when necessary, both in downlink (DL),i.e., from base station to wireless device, and uplink (UL), i.e., fromwireless device to base station. To support multiple-layer multipleinput multiple output (MIMO) transmission, multiple orthogonal DM-RSports can be scheduled, one for each layer. Orthogonality is achieved byfrequency division multiplexing (FDM) (comb structure), time divisionmultiplexing (TDM) and code division multiplexing (CDM) (with cyclicshift of the root sequence or orthogonal cover codes). The basic DM-RSpattern is front loaded, as the DM-R.S design takes into account theearly decoding requirement to support low-latency applications. Forlow-speed scenarios, DM-RS uses low density in the time domain. However,for high-speed scenarios, the time density of DM-RS is increased totrack fast changes in the radio channel. FIGS. 1 and 2 illustrate thepotential DM-RS resource mapping in the frequency-time grid for lowDoppler and high Doppler scenarios, respectively, in the transmissionslot.

Another challenge that NR faces is the radio-frequency (RF) impairmentswhen wireless systems operate in the millimeter (mm) wave band,specifically, the effects of phase noise produced by the localoscillators. The degradation produced by phase noise increases as thecarrier frequency increases, so that the physical layer of NR operatingin mmWave frequencies has to be robust to phase noise in order toachieve good performance. Hence, there is a need for a new referencesignal called the phase tracking reference signal (PT-RS). Such signalcan be used both for mitigation of the phase noise-induced common phaseerror (CPE), experienced equally on all subcarriers within an OFDMsymbol, and inter-carrier interference (ICI) caused by the loss oforthogonality between subcarriers.

The PT-RS may be needed both in uplink and downlink. It is foreseen thatthis signal can be used for both fine carrier frequency-synchronizationand phase noise compensation. This signal is assumed to be present andneeded only at high carder frequencies, while the other properties ofthe DM-RS can remain somewhat unchanged. An example of adding a PT-RS athigh carrier frequencies is depicted in FIG. 3.

Different modulation and coding schemes (MCS) offer different robustnessagainst the effects of phase noise, as shown in FIGS. 4 and 5.Therefore, the time density of PT-RS for a specific wireless device (WD)can be configured according to the scheduled MCS.

The problems of the existing solution can be summarized as follows:

PT-RS is a new reference-signal introduced to NR, which may co-existwith DM-RS in certain scenarios;

Each type of reference signal needs to reserve its own resource in thetime-frequency grid;

Prior art solutions propose a joint design for DM-RS and PT-RS but thedesign is limited to the case in which just one DM-RS instance isscheduled in the slot; and

Pilot contamination may happen such that the overhead of the totalresources used by reference signals needs to be controlled.

SUMMARY

The proposed solution for the joint design of DM-RS and PT-RS may bebased on the conditions that the PT-RS mapping in the time domain maydepend at least on the following:

-   -   The position of the front-loaded DM-RS in the slot for an        antenna port in which PT-RS is mapped;    -   Required time density in the time domain for PT-RS;    -   The position of the first symbol scheduled for data transmission        in the transmission slot; and    -   The position of the last symbol scheduled for data transmission        in the transmission slot.

-   The proposed solution may also include joint mapping of DM-RS and    PT-RS. The position of the additional DM-RS in the slot may depend    on the PT-RS which is mapped.

-   One aspect is that the PT-RS resource can be aligned with the first    DM-RS in the slot when PT-RS is scheduled. Furthermore, when the    additional DM-RS and PT-RS both exist in the resource grid, the    additional DM-RS position may align with the PT-RS position.

In some embodiments, a method for use in a radio node in a wirelesscommunication system for one of transmitting and receiving a phasetracking-reference signal (PT-RS) is provided. The method includesobtaining information about a position in a time domain of a scheduledfirst demodulation reference signal (DM-RS) in a slot. The method alsoincludes one of transmitting and receiving the PT-RS within the slot,where the position of the PT-RS depends on the position in the timedomain of the scheduled first DM-RS.

In some embodiments, the obtaining comprises one of receivinginformation about and determining the position in the time domain of thescheduled first DM-RS. In some embodiments, the method further includesobtaining information about a position of a first time symbol in a slotscheduled for data transmission. In some embodiments, the method alsoincludes obtaining information about a position of a last time symbol inthe slot scheduled for data transmission. In some embodiments, themethod also includes obtaining information indicating a scheduledmodulation and coding scheme, MCS, and transmitting the PT-RS with atime density based on the scheduled MCS. In some embodiments, the timedensity is one 1, ½ and ¼. In some embodiments, the method includesmapping the PT-RS to resource elements, REs, in the slot based on one ormore of a position of the scheduled first DM-RS, a scheduled MCS, arequired time-density, a position of the first time symbol scheduled fordata transmission and a position of the last time symbol scheduled fordata transmission. In some embodiments, the first DM-RS is scheduled inresource elements, REs, which span several subcarriers in frequency andat least one time symbol of the slot in time, while the PT-RS is one oftransmitted and received in REs which span at least one subcarrier infrequency and multiple time symbols of the slot in time. In someembodiments, a physical resource block, PRB, of the slot has 12subcarriers in the frequency domain and one of 12 and 14 time symbols inthe time domain. In some embodiments, the radio node is one of a WD anda network node. According to another aspect, a radio node in a wirelesscommunication system configured for one of transmitting and receiving aPT-RS is provided. The radio node includes processing circuitryconfigured to obtain information about a position in a time domain of ascheduled first DM-RS in a slot. The processing circuitry is furtherconfigured to one of transmit and receive the PT-RS within the slot,where the position of the PT-RS depends on the position in the timedomain of the scheduled first DM-RS.

According to this aspect, in some embodiments, the obtaining comprisesone of receiving information about and determining the position in thetime domain of the scheduled first DM-RS. In some embodiments, theprocessing circuitry is further configured to obtain information about aposition of a first time symbol in a slot scheduled for datatransmission, and obtain information about a position of a last timesymbol in the slot scheduled for data transmission. In some embodiments,the processing is further configured to obtain information indicating ascheduled modulation and coding scheme, MCS, and transmit the PT-RS witha time density based on the scheduled MCS. In some embodiments, the timedensity is one 1, ½ and ¼. In some embodiments, the processing circuitryis further configured to map the PT-R.S to resource elements, REs, inthe slot based on one or more of a position of the scheduled firstDM-RS, a scheduled MCS. a required time-density, a position of the firsttime symbol scheduled for data transmission and a position of the lasttime symbol scheduled for data transmission. In some embodiments, thefirst DM-RS is scheduled in resource elements, REs, which span severalsubcarriers in frequency and at least one time symbol of the slot intime, while the PT-RS is one of transmitted and received in REs whichspan at least one subcarrier in frequency and multiple time symbols ofthe slot in time. In some embodiments, a physical resource block, PRB,of the slot has 12 subcarriers in the frequency domain and one of 12 and14 time symbols in the time domain. In some embodiments, the radio nodeis one of a WD and a network node.

According to another aspect, a radio node in a wireless communicationsystem configured for one of transmitting and receiving a PT-RS isprovided. The radio node includes demodulation reference signal, DM-RS,position module configured to obtain information about a position in atime domain of a scheduled first DM-RS in a slot. The radio node furtherincludes a PT-RS transceiver module configured to one of transmit andreceive the PT-RS within the slot, where the position of the PT-RSdepends on the position in the time domain of the scheduled first DM-RS.In some embodiments, the first DM-RS is scheduled in resource elements,REs, which span several subcarriers in frequency and at least one singletime symbol of the slot in time, while the PT-RS is one of transmittedand received in REs which span at least one subcarrier in frequency andmultiple time symbols of the slot in time.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of embodiments described herein, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 shows possible DM-RS patterns for NR that support early decodingfor low Doppler;

FIG. 2 shows possible DM-RS patterns for NR that support early decodingfor high Doppler;

FIG. 3 shows addition of PT-RS at high carrier frequencies;

FIG. 4 shows evaluation results for 16 QAM (¾) MCS;

FIG. 5 shows evaluation results for 64 QAM (⅚) MCS;

FIG. 6 is a block diagram of a wireless communication system constructedin accordance with principles set forth herein;

FIG. 7 is a block diagram of a network node constructed in accordancewith princip set forth herein;

FIG. 8 is a block diagram of an alternative embodiment of a network nodeconstructed in accordance with principles set forth herein;

FIG. 9 is a block diagram of a wireless device constructed in accordancewith principles set forth herein;

FIG. 10 is a block diagram of an alternative embodiment of a wirelessdevice constructed in accordance with principles set forth herein; and

FIG. 11 is a flowchart of an exemplary process for joint scheduling ofDM-RS and PT-RS that can be performed in the wireless device and/or thenetwork node.

FIG. 12 is a flowchart of an exemplary process for scheduling DM-RS andPT-RS;

FIG. 13 is a flowchart of an exemplary process for transmitting andreceiving a phase tracking reference signal (PT-RS);

FIG. 14 shows a single DM-RS instance with aligned DM-RS and PT-RS withtime density 1;

FIG. 15 shows a single front loaded DM-RS with aligned DM-RS and PT-RSwith time density ½;

FIG. 16 shows a double front loaded DM-RS with aligned DM-RS and PT-RSwith time density ½;

FIG. 17 shows front loaded DM-RS pattern with additional DM -RS andPT-RS with time density 1;

FIG. 18 shows front loaded DM-R.S pattern with additional DM-R.S andPT-RS with time density ½;

DETAILED DESCRIPTION

Before describing in detail exemplary embodiments, it is noted that theembodiments reside primarily in combinations of apparatus components andprocessing steps related to scheduling phase tracking reference signals,PT-RS, jointly with demodulation reference signals, DM-RS. Accordingly,the system and method components have been represented Where appropriateby conventional symbols in the drawings, showing only those specificdetails that are pertinent to understanding the embodiments of thepresent disclosure so as not to obscure the disclosure with details thatwill be readily apparent to those of ordinary skill in the art havingthe benefit of the description herein.

As used herein, relational terms, such as “first” and “second,” “top”and “bottom,” and the like, may be used solely to distinguish one entityor element from another entity or element without necessarily requiringor implying any physical or logical relationship or order between suchentities or elements.

An indication generally may explicitly and/or implicitly indicate theinformation it represents and/or indicates. Implicit indication may forexample be based on position and/or resource used for transmission.Explicit indication may for example be based on a parametrization withone or more parameters, and/or one or more index or indices, and/or oneor more hit patterns representing the information. It may in particularbe considered that control signaling as described herein, based on theutilized resource sequence, implicitly indicates the control signalingtype.

The term signal used herein can be any physical signal or physicalchannel. Examples of physical signals are reference signal such as PSS,SSS, CRS, PRS etc. The term physical channel (e.g., in the context ofchannel reception) used herein is also called as channel. Examples ofphysical channels are MIB, PBCH, NPBCH, PDCCH, PDSCH, sPUCCH, sPDSCH.sPUCCH, sPUSCH, MPDCCH, NPDCCH, NPDSCH, E-PDCCH, PUSCH, PUCCH, NPUSCHetc. These terms/abbreviations may be used according to 3GPP standardlanguage, in particular according to LTE and/or NR.

It may be considered for cellular communication there is provided atleast one uplink (UL) connection and/or channel and/or carrier and atleast one downlink (DL) connection and/or channel and/or carrier, e. viaand/or defining a cell, which may be provided by a network node, inparticular a base station or eNodeB. An uplink direction may refer to adata transfer direction from a terminal to a network node, e.g., basestation and/or relay station. A downlink direction may refer to a datatransfer direction from a network node, e.g., base station and/or relaynode, to a terminal. UL and DL may be associated to different frequencyresources, e.g., carriers and/or spectral bands. A cell may comprise atleast one uplink carrier and at least one downlink carrier, which mayhave different frequency bands. A network node, e.g., a base station,gNB or eNodeB, may be adapted to provide and/or define and/or controlone or more cells, e.g., a PCell and/or a LA cell.

Transmitting in downlink may pertain to transmission from the network ornetwork node to the terminal. Transmitting in uplink may pertain totransmission from the terminal to the network or network node,Transmitting in sidelink may pertain to (direct) transmission from oneterminal to another. Uplink, downlink and sidelink (e.g., sidelinktransmission and reception) may be considered communication directions.In some variants, uplink and downlink may also be used to describedwireless communication between network nodes, e.g. for wireless backhauland/or relay communication and/or (wireless) network communication forexample between base stations or similar network nodes, in particularcommunication terminating at such. it may be considered that backhauland/or relay communication and/or network communication is implementedas a form of sidelink or uplink communication or similar thereto.

Generally, configuring may include determining configuration datarepresenting the configuration and providing, e.g. transmitting, it toone or more other nodes (parallel and/or sequentially), which maytransmit it further to the radio node (or another node, which may berepeated until it reaches the wireless device) Alternatively, oradditionally, configuring a radio node, e.g., by a network node or otherdevice, may include receiving configuration data and/or data pertainingto configuration data, e.g., from another node like a network node 16,which may be a higher-level node of the network, and/or transmittingreceived configuration data to the radio node. Accordingly, determininga configuration and transmitting the configuration data to the radionode may be performed by different network nodes or entities, which maybe able to communicate via a suitable interface, e.g., an X2 interfacein the case of LTE or a corresponding interface for NR. Configuring aterminal (e.g. WD) may comprise scheduling downlink and/or uplinktransmissions for the terminal, e.g. downlink data and/or downlinkcontrol signaling and/or DCI and/or uplink control or data orcommunication signaling, in particular acknowledgement signaling, and/orconfiguring resources and/or a resource pool therefor. In particular,configuring a terminal (e.g. WD) may comprise configuring the WD toperform certain measurements on certain subframes or radio resources andreporting such measurements according to embodiments of the presentdisclosure

Signaling may comprise one or more signals and/or symbols. Referencesignaling may comprise one or more reference signals and/or symbols.Data signaling may pertain to signals and/or symbols containing data, inparticular user data and/or payload data and/or data from acommunication layer above the radio and/or physical layer/s. It may beconsidered that demodulation reference signaling comprises one or moredemodulation signals and/or symbols. Demodulation reference signalingmay in particular comprise DM-RS according to 3GPP and/or NR and/or LTEtechnologies. Demodulation reference signaling may generally beconsidered to represent signaling providing reference for a receivingdevice like a terminal to decode and/or demodulate associated datasignaling or data. Demodulation reference signaling may be associated todata or data signaling, in particular to specific data or datasignaling. It may be considered that data signaling and demodulationreference signaling are interlaced and/or multiplexed, e.g. arranged inthe same time interval covering e.g. a subframe or slot or symbol,and/or in the same time-frequency resource structure like a resourceblock. A resource element may represent a smallest time-frequencyresource, e.g. representing the time and frequency range covered by onesymbol or a number of bits represented in a common modulation. Aresource element may e.g. cover a symbol time length and a subcarrier,in particular in 3GPP and/or NR and/or LTE standards. A datatransmission may represent and/or pertain to transmission of specificdata, e.g. a specific block of data and/or transport block. Generally,demodulation reference signaling may comprise and/or represent asequence of signals and/or symbols, which may identify and/or define thedemodulation reference signaling.

Data or information may refer to any kind of data, in particular any oneof and/or any combination of control data or user data or payload data.Control information (which may also be referred to as control data) mayrefer to data controlling and/or scheduling and/or pertaining to theprocess of data transmission and/or the network or terminal operation.

FIG. 6 is a block diagram of a wireless communication network configuredaccording to principles set forth herein. The wireless communicationnetwork 10 includes a cloud 12 which may include the Internet and/or thepublic switched telephone network (PSTN). Cloud 12 may also serve as abackhaul network of the wireless communication network 10. The wirelesscommunication network 10 includes one or more network nodes 14A and 14B,which may communicate directly via an X2 interface in LTE embodiments,and are referred to collectively as network nodes 14. It is contemplatedthat other interface types can be used for communication between networknodes 14 for other communication protocols such as New Radio (NR). Thenetwork nodes 14 may serve wireless devices 16A and 16B, referred tocollectively herein as wireless devices 16. Note that, although only twowireless devices 16 and two network nodes 14 are shown for convenience,the wireless communication network 10 may typically include many morewireless devices (WDs) 16 and network node 14. Further, in someembodiments, WDs 16 may communicate directly using what is sometimesreferred to as a side link connection.

The tem “wireless device” or mobile terminal used herein may refer toany type of wireless device communicating with a network node 14 and/orwith another wireless device 16 in a cellular or mobile communicationsystem 10. Examples of a wireless device 16 are user equipment (UE),target device, device to device (D2D) wireless device, machine typewireless device or wireless device capable of machine to machine (M2M)communication, PDA, tablet, smart phone, laptop embedded equipped (LEE),laptop mounted equipment (LME), USB dangle, etc.

The tern “network node” used herein may refer to any kind of radio basestation in a radio network which may further comprise any basetransceiver station (BTS), base station controller (BSC), radio networkcontroller (RNC), evolved Node B (eNB or eNodeB), NR. gNodeB, NR gNB,Node B, multi-standard radio (MSR) radio node such as MSR BS, relaynode, donor node controlling relay, radio access point (AP),transmission points, transmission nodes, Remote Radio Unit (RRU) RemoteRadio Head (RRH), nodes in distributed antenna system (DAS), etc.

Although embodiments are described herein with reference to certainfunctions being performed by network node 14, it is understood that thefunctions can be performed in other network nodes and elements. It isalso understood that the functions of the network node 14 can bedistributed across network cloud 12 so that other nodes can perform oneor more functions or even parts of functions described herein. Also,functions described herein as being performed by a network node 14 mayalso be performed by a wireless device 16.

The network node 14 has DM-RS position information 30 that may be storedin memory. The DM-RS position information includes information about aposition in the time domain of a scheduled first DM-RS in a slot. Thenetwork node 14 also has a PT-RS transceiver 28 configured to transmitor receive a PT-RS within the slot, where the position of the PT-RSdepends on a position of the DM-RS. Similarly, the wireless device 16may include DM-RS position information 50 and a PT-RS transceiver 48that perform the same functions as the DM-RS position memory 30 and thePT-RS transceiver 28, respectively.

FIG. 7 is a block diagram of a network node 14 configured for jointscheduling of DM-RS and PT-RS. The network node 14 has processingcircuitry 22. In some embodiments, the processing circuitry may includea memory 24 and processor 26, the memory 24 containing instructionswhich, when executed by the processor 26, configure processor 26 toperform the one or more functions described herein. In addition to atraditional processor and memory, processing circuitry 22 may includeintegrated circuitry for processing and/or control, e.g., one or moreprocessors and/or processor cores and/or FPGAs (Field Programmable GateArray) and/or ASICs (Application Specific Integrated Circuitry).

Processing circuitry 22 may include and/or be connected to and/or beconfigured for accessing (e.g., writing to and/or reading from) memory24, which may include any kind of volatile and/or non-volatile memory,e.g., cache and/or buffer memory and/or RAM (Random Access Memory)and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM(Erasable Programmable Read-Only Memory). Such memory 24 may beconfigured to store code executable by control circuitry and/or otherdata, e.g., data pertaining to communication, e.g., configuration and/oraddress data of nodes, etc. Processing circuitry 22 may be configured tocontrol any of the methods described herein and/or to cause such methodsto he performed, e.g., by processor 26. Corresponding instructions maybe stored in the memory 24, which may be readable and/or readablyconnected to the processing circuitry 22. In other words, processingcircuitry 22 may include a controller, which may include amicroprocessor and/or microcontroller and/or FPGA Programmable GateArray) device and/or ASIC (Application Specific Integrated Circuit)device. It may be considered that processing circuitry 22 includes ormay be connected or connectable to memory, which may be configured to beaccessible for reading and/or writing by the controller and/orprocessing circuitry 22.

The memory 24 is configured to store DM-RS position information 30 andPT-RS schedule information 32. The processor 26 implements a DM-RSposition obtainer 18 configured to obtain information about a positionin the time domain of a scheduled first DM-R.S in a slot. The processor26 may also implement a PT-RS scheduler 20 configured to schedule thePT-RS in the slot. A transceiver 28 is configured to transmit the PT-RSto a wireless device 16 or receive the PT-RS from the wireless device16, where the position of the PT-RS depends on the position of the firstDM-RS.

FIG. 8 is a block diagram of an alternative embodiment of a network node14 configured for joint scheduling of DM-RS and PT-RS. The memory module25 is configured to store DM-R.S position information 30 and PT-RSschedule information 32. The DM-RS position obtainer module 19 isconfigured to obtain information about a position in the time domain ofa scheduled first DM-RS in a slot. The PT-RS scheduler module 21 isconfigured to schedule the PT-RS in the slot. A transceiver module 29 isconfigured to transmit the PT-RS to a wireless device 16 or receive aPT-RS from the wireless device 16, where the position of the PT-RSdepends on the position of the first DM-RS.

Note that the same components shown in FIG. 7 in the network node 14 canbe implemented in a wireless device 16 for joint scheduling of DM-RS andPT-RS by the wireless device 16 for transmission on the uplink. Thus,the wireless device 16 may have a DM-RS position obtainer 58 and a PT-RSscheduler 60 for joint scheduling of the DM-RS and PT-RS on the uplink.

Accordingly, FIG. 9 is a block diagram of a wireless device 16configured for joint scheduling of DM-RS and PT-RS. The wireless device16 has processing circuitry 42. In some embodiments, the processingcircuitry may include a memory 44 and processor 46, the memory 44containing instructions which, when executed by the processor 46,configure processor 46 to perform the one or more functions describedherein. In addition to a traditional processor and memory, processingcircuitry 42 may include integrated circuitry for processing and/orcontrol, e.g., one or more processors and/or processor cores and/orFPGAs (Field Programmable Gate Array) and/or ASICs (Application SpecificIntegrated Circuitry).

Processing circuitry 42 may include and/or be connected to and/or beconfigured for accessing (e.g., writing to and/or reading from) memory44, which may include any kind of volatile and/or non-volatile memory,e.g., cache and/or buffer memory and/or RAM (Random Access Memory)and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM(Erasable Programmable Read-Only Memory). Such memory 44 may beconfigured to store code executable by control circuitry and/or otherdata, e.g., data pertaining to communication, e.g., configuration and/oraddress data of nodes, etc. Processing circuitry 42 may be configured tocontrol any of the methods described herein and/or to cause such methodsto be performed, e.g., by processor 46. Corresponding instructions maybe stored in the memory 44, which may be readable and/or readablyconnected to the processing circuitry 42. In other words, processingcircuitry 42 may include a controller, which may include amicroprocessor and/or microcontroller and/or FPGA

Programmable Gate Array) device and/or ASIC (Application SpecificIntegrated Circuit) device. It may be considered that processingcircuitry 42 includes or may be connected or connectable to memory,which may be configured to be accessible for reading and/or writing bythe controller and/or processing circuitry 42.

The memory 44 is configured to store DM-RS position information 50 and

PT-RS schedule information 52. The processor 46 implements a DM-RSposition obtainer 58 configured to obtain information about a positionin the time domain of a scheduled first DM-RS in a slot. The processor46 also implements a PT-RS scheduler 60 configured to schedule the PT-RSin the slot. A transceiver 48 is configured to transmit the PT-RS to anetwork node 14 or receive a PT-RS from the network node 14, where theposition of the PT-RS depends on the position in the time domain of thescheduled first DM-RS.

FIG. 1.0 is a block diagram of an alternative embodiment of a wirelessdevice 16 configured for joint scheduling of DM-RS and PT-RS. The memorymodule 45 is configured to store DM-RS position information 50 and PT-RSschedule information 52. The DM-RS position obtainer module 59 isconfigured to obtain information about a position in the time domain ofa scheduled first DM-RS in a slot. The PT-RS scheduler module 61 isconfigured to schedule the PT-RS in the slot. A transceiver module 49 isconfigured to transmit the PT-RS to a network node 14 or receive a PT-RSfrom the network node 14, where the position of the PT-RS depends on theposition in the time domain of the scheduled first DM-RS.

FIG. 11 is a flowchart of an exemplary process for joint scheduling ofDM-RS and PTRS. This process can be performed in the network node 14and/or in the wireless device 16. The process includes scheduling, viathe processor 26, 46, the DM-RS in a time-frequency resource grid at aplurality of frequencies in a same time slot (block S90). The processalso includes scheduling, via the PT-RS scheduler 20, 60, the PT-RS inthe time-frequency grid at a plurality of time slots at a samefrequency, the time slots at which the PT-RS are scheduled depending ona position of the DM-RS (block S92).

An advantage of some embodiments is that the total reference signaloverhead can be reduced to avoid pilot contamination, while achievingthe required estimation quality. The main steps of an embodiment of theproposed joint design of DM-RS and PT-RS position are shown in FIG. 12.The process includes determining, via the PT-RS scheduler 20, 60 a PT-RStime density according to a scheduled MCS (block S100). The process alsoincludes determining, via the DM-RS position obtainer, 18, 58, aposition of a front loaded DM-RS (block S102). The process furtherincludes determining, via the processor 26, 46, a position of the firstand last symbol scheduled for data transmission (block S104). Then thesolution proposed and described herein is used to obtain a map of thePT-RS in a slot (block S106). If there are additional instances of theDM-RS (block S108), then the proposed solution is used to obtain theDM-RS map (block S110). Otherwise, the process concludes.

FIG. 13 is a flowchart of an exemplary process for transmitting orreceiving a phase tracking reference signal (PT-RS). The processincludes obtaining, via the DM-RS position obtainer 18, 48. informationabout a position in a time domain of a scheduled first demodulationreference signal, DM-RS in a slot (block S120). The position may beobtained from the WD 16 via radio resource control scheduling of theDM-RS. The process also includes one of transmitting and receiving, viathe PT-RS transceiver 28, 48, the PT-RS within the slot, where theposition of the PT-RS depends on the position in the time domain of thescheduled first DM-RS (block S122).

Having described the general process flow of arrangements of thedisclosure and having provided examples of hardware and softwarearrangements for implementing the processes and functions of thedisclosure, the sections below provide details and examples ofarrangements for implementing embodiments of the disclosure and fortransmitting and receiving PT-RS.

The proposed solution may have at least some of the following benefits:

a reduction in the total overhead of the reference signals when DM-RSand

PT-RS are both scheduled;

a common design of both reference signals which adapts with the actualposition of the front-loaded DM-RS in the slot; and both types ofreference signal can provide desired estimation quality.

The process may be described as follows, in some embodiments. Consider aslot-based transmission. A slot-interval may be L OFDM symbol length,e.g., 7 or 14 symbols. The symbol index has range [1:]. The mapping ofthe PT-RS in the time domain is determined by:

X_(REF)=min(D_(FL)), where D_(FL) represents the set containing theposition of the front-loaded DM-RS.

Δ_(PTRS), the distance between PT-RS instances, which is inverselyproportional to the PT-RS time density.

D₀≥1, the first symbol scheduled for data transmission in the slot.

D₁≥L, the last symbol scheduled for data transmission in the slot.

-   Let P represent the set containing the time position of PT-RS in the    transmission slot. In order to obtain an aligned design for    front-loaded DM-RS and PT-RS, P may be defined as follows

P={n ∈

/D₀ ≤n≤D₁and (n−X_(REF)) mod Δ_(PTRS)=01}

-   Let D represent the set of potential positions of the additional    DM-RS in the slot. In order to obtain an aligned design for DM-RS    and PT-RS, D may be defined as follows

D={n ∈P and n>X_(REF)}

-   So the DM-RS instances are a subset of the PT-RS instances, offering    an aligned design for PT RS and DM-RS. To summarize, the overall    criteria of a proposed solution according to some embodiments may be    expressed as:

P, D=arg max|P∩ D|

subject to X_(REF), Δ_(PTRS,) , D₀, D₁.

Embodiment: Front loaded DM-RS and PT-RS with time density 1

In FIG. 14, an example of joint design for PT-RS with time density 1 andsingle front-loaded DMRS instance pattern is shown.

In FIG. 15, an example of joint design for single front-loaded DM-RSpattern and PT-RS with time density ½ is shown. It can be seen that byusing a joint design for DM-RS and PT-RS, the reference signal overheadin the slot may be kept low (because the DM-RS instance can be re-usedfor phase noise estimation, replacing PT-RS). Without the joint designthe reference signal time density could be higher than ½.

FIG. 16 is an example of a joint design for a double front-loaded DMRSpattern and PT-RS with time density ½. A benefit of the proposed jointdesign in some embodiments is that the PT-RS map does not change forsingle and front-loaded DMRS pattern.

Embodiment: Front-loaded DM-RS with additional DM-RS instance and PT-RSwith time density 1

In FIG. 17, an example of a joint design for front loaded DM-RS patternwith additional DM-RS and PT-RS with time density 1 is shown.

Embodiment: Front-loaded DM-RS with additional DM-RS instance and PT-RSwith time density ½

In FIG. 18, an example of a joint design for a front-loaded DMRS patternwith an additional DM-RS instance and PT-RS with time density ½ isshown. By using a joint design for DM-R.S and PT-RS, the referencesignal overhead in the time domain in the slot may be kept low becausethe DM-RS instances can be re-used for phase noise estimation, replacingPT-RS). Without the joint design the reference signal time density couldbe higher than ½.

An advantage of some embodiments is that a joint design of DM-RS andPT-RS can reduce the overhead of the reference signals in the timedomain while keeping accuracy in the estimations based on the referencesignals.

The PT-RS is usually scheduled for only one antenna port (associatedwith one DMRS port), i.e., there is no multiplexing of resources used bythe PT-RS, which paves the way for the alignment of DM-RS and PT-RSresource elements to reduce overhead. The density of the PT-RS dependson the modulation and coding scheme (MCS), which provides the freedom ofplacing the PT-RS in the resource grid using different time-offsets withequal performance. Because the PT-RS is a time domain signal which spansthe resource grid with a certain density, it also provides a set ofpositions with which the DM-RS can align. A result is that when theadditional DMRS are scheduled, there exists at least one PT-RS resourceposition that provides a desired channel estimation quality.

In some embodiments, a method for use in a radio node 14, 16 in awireless communication system for one of transmitting and receiving aphase tracking-reference signal, PT-RS, is provided. The method includesobtaining (block S120) information about a position in a time domain ofa scheduled first demodulation reference signal, DM-RS in a slot. Theposition information may be obtained, for example from the wirelessdevice 16 via radio resource control scheduling of the DM-RS. The methodalso includes one of transmitting and receiving (block S122) the PT-RSwithin the slot, where the position of the PT-RS depends on the positionin the time domain of the scheduled first DM-RS.

In some embodiments, the obtaining comprises one of receivinginformation about and determining the position in the time domain of thescheduled first DM-RS. In some embodiments, the method further includesobtaining information about a position of a first time symbol in a slotscheduled for data transmission. In some embodiments, the method alsoincludes obtaining information about a position of a last time symbol inthe slot scheduled for data transmission. In some embodiments, themethod also includes obtaining information indicating a scheduledmodulation and coding scheme, MCS, and transmitting the PT-RS with atime density based on the scheduled MCS. This may be the case for OFDM,whereas for DFTS-OFDM waveforms, higher layer messaging may be used toindicate the time density. In some embodiments, the time density is one1, ½ and ¼. In some embodiments, the method includes mapping the PT-RSto resource elements, REs, in the slot based on one or more of aposition of the scheduled first DM-RS, a scheduled MCS, a requiredtime-density, a position of the first time symbol scheduled for datatransmission and a position of the last time symbol scheduled for datatransmission. In sonie embodiments, the first DM-RS is scheduled inresource elements, REs, which span several subcarriers in frequency andone or two time symbols of the slot in time, while the PT-RS is one oftransmitted and received in REs which span at least one subcarrier infrequency and multiple time symbols of the slot in time. in someembodiments, a physical resource block, PRB, of the slot has 12subcarriers in the frequency domain and one of 12 and 14 time symbols inthe time domain. In some embodiments, the radio node 14, 16 is one of aWD and a network node. In some embodiments, an additional DM-RS isscheduled in the same slot as the first DM-RS and PT-RS, and theposition of the second DM-RS depends on the position of the PT-RS. Insome embodiments, the PT-RS is only transmitted in the mm wavelengthhigh frequency band.

According to another aspect, a radio node 14, 16 in a wirelesscommunication system configured for one of transmitting and receiving aphase tracking-reference signal, PT-RS, is provided. The radio node 14,16 includes processing circuitry configured to obtain information abouta position in a time domain of a scheduled first demodulation referencesignal, DM-RS in a slot. The processing circuitry 22, 42 is furtherconfigured to one of transmit and receive the PT-RS within the slot,where the position of the PT-RS depends on the position in the timedomain of the scheduled first DM-RS.

According to this aspect, in some embodiments, the obtaining comprisesone of receiving and determining information about the position in thetime domain of the scheduled first DM-RS. In some embodiments, theprocessing circuitry 22, 42 is further configured to obtain informationabout a position of a first time symbol in a slot scheduled for datatransmission, and obtain information about a position of a last timesymbol in the slot scheduled for data transmission. In some embodiments,the processing circuitry 22, 42 is further configured to obtaininformation indicating a scheduled modulation and coding scheme, MCS,and transmit the PT-RS with a time density based on the scheduled MCS.In some embodiments, the time density is one 1, ½, and ¼. A and In someembodiments, the processing circuitry 22, 42 is further configured tomap the PT-RS to resource elements, REs, in the slot based on one ormore of a position of the scheduled first DM-RS, a scheduled MCS, arequired time-density, a position of the first time symbol scheduled fordata transmission and a position of the last time symbol scheduled fordata transmission. In some embodiments, the first DM-RS is scheduled inresource elements, REs, which span several subcarriers in frequency andat least one time symbol of the slot in time, while the PT-RS is one oftransmitted and received in REs which span at least one subcarrier infrequency and multiple time symbols of the slot in time. In someembodiments, a physical resource block, PRB, of the slot has 12subcarriers in the frequency domain and one of 12 and 14 time symbols inthe time domain. in some embodiments, the radio node 14, 16 is one of aWD and a network node.

According to another aspect, a radio node 14, 16 in a wirelesscommunication system configured for one of transmitting and receiving aphase tracking-reference signal. PT-RS is provided. The radio node 14,16 includes demodulation reference signal, DM-RS, position obtainermodule 19, 59 configured to obtain information about a position in atime domain of a scheduled first demodulation reference signal, DM-RS ina slot. The radio node 14, 16 further includes a PT-RS transceivermodule 29, 49 configured to one of transmit and receive the PT-RS withinthe slot, where the position of the PT-RS depends on the position in thetime domain of the scheduled first DM-RS. In sonic embodiments, thefirst DM-RS is scheduled in resource elements, REs, which span severalsubcarriers in frequency and at least one time symbol of the slot intime, while the PT-RS is one of transmitted and received in REs whichspan at least one subcarrier in frequency and multiple time symbols ofthe slot in time.

Some embodiments include the following:

-   Embodiment 1. A method for scheduling phase tracking reference    signals, PT-RS, jointly with demodulation reference signals, DM-RS,    the method comprising:

scheduling the DM-RS in a time-frequency resource grid at a plurality offrequencies in a same time slot; and

scheduling the PT-RS in the time-frequency grid at a plurality of timeslots at a same frequency, the time slots at which the PT-RS arescheduled depending on a position of the DM-RS.

-   Embodiment 2. The method of Embodiment 1, wherein a time-density of    the PT-RS depends on a selected modulation and coding scheme.-   Embodiment 3. The method of any of Embodiments 1 and 2, wherein the    time-density is one half.-   Embodiment 4. The method of any of Embodiments 1-3, wherein the    DM-RS is single front loaded.-   Embodiment 5. The method of any of Embodiments 1-3, wherein the    DM-RS is double front loaded.-   Embodiment 6, The method of any of Embodiments 1-5, wherein the    method is performed by a network node.-   Embodiment 7. The method of any of Embodiments 1-5, wherein the    method is performed by a wireless device.-   Embodiment 8. A network node configured to schedule phase tracking    reference signals, PT-RS, jointly with demodulation reference    signals, DM-RS, the network node comprising:    -   processing circuitry configured to:        -   schedule the DM-RS in a time-frequency resource grid at a            plurality of frequencies in a same time slot; and        -   schedule the PT-RS in the time-frequency grid at a plurality            of time slots at a same frequency, the time slots at which            the PT-RS are scheduled depending on a position of the            DM-RS.-   Embodiment 9. The network node of Embodiments 8, wherein a    time-density of the PT-R.S depends on a selected modulation and    coding scheme.-   Embodiment 10, The network node of any of Embodiments 8 and 9,    wherein the time-density is one half.-   Embodiment 11. The network node of any of Embodiments 8-10, wherein    the DM-RS is single front loaded.-   Embodiment 12. The network node of any of Embodiments 8-10, wherein    the DM-RS is double front loaded.-   Embodiment 13. A network node configured to schedule phase tracking    reference signals, PT-RS, jointly with demodulation reference    signals, DM-RS, the network node comprising:

a DM-RS scheduling module configured to schedule the DM-RS in atime-frequency resource grid at a plurality of frequencies in a sametime slot; and a PT-RS scheduling module configured to schedule thePT-RS in the time-frequency grid at a plurality of time slots at a samefrequency, the time slots at which the PT-RS are scheduled depending ona position of the DM-RS.

-   Embodiment 14. A wireless device configured to schedule phase    tracking reference signals, PT-RS, jointly with demodulation    reference signals, DM-RS, the wireless device comprising:

processing circuitry configured to:

-   -   schedule the DM-RS in a time-frequency resource grid at a        plurality of frequencies in a same time OM and    -   schedule the PT-RS in the time-frequency grid at a plurality of        time slots at a same frequency, the time slots at which the        PT-RS are scheduled depending on a position of the DM-RS.

-   Embodiment 15. The network node of claim 14, wherein a time-density    of the PT-R.S depends on a selected modulation and coding scheme.

-   Embodiment 16, The network node of any of Embodiments 14 and 15,    wherein the time-density is one half.

-   Embodiment 17. The network node of any of Embodiments 14-16, wherein    the DM-RS is single front loaded.

-   Embodiment 18. The network node of any of Embodiments 14-16, wherein    the DM-RS is double front loaded.

-   Embodiment 19. A wireless device configured to schedule phase    tracking reference signals, PT-RS, jointly with demodulation    reference signals, DM-RS, the wireless device comprising:

a DM-RS scheduling module configured to schedule the DM-RS in atime-frequency resource grid at a plurality of frequencies in a sametime slot; and

a PT-RS scheduling module configured to schedule the PT-RS in thetime-frequency grid at a plurality of time slots at a same frequency,the time slots at which the PT-RS are scheduled depending on a positionof the DM-RS.

Abbreviation Explanation 3GPP Third Generation Partnership Project eNBEnhanced NodeB CRS Cell-Specific Reference Signal DM-RS De-ModulationReference Signal DCI Downlink Control Information LTE Long TermEvolution MIMO Multiple Input Multiple Output PT-RS Phase TrackingReference Signal RS Reference Signal TM Transmission Mode TTITransmission Time Interval UE User Equipment URLLC Ultra-reliable lowlatency communications WD Wireless Device

As will be appreciated by one of skill in the art, the conceptsdescribed herein may be embodied as a method, data processing system,and/or computer program product. Accordingly, the concepts describedherein may take the form of an entirely hardware embodiment, an entirelysoftware embodiment or an embodiment combining software and hardwareaspects all generally referred to herein as a “circuit” or “module.”Furthermore, the disclosure may take the form of a computer programproduct on a tangible computer usable storage medium having computerprogram code embodied in the medium that can be executed by a computer.Any suitable tangible computer readable mediwn may be utilized includinghard disks, CD-ROMs, electronic storage devices, optical storagedevices, or magnetic storage devices.

Some embodiments are described herein with reference to flowchartillustrations and/or block diagrams of methods, systems and computerprogram products. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer (to create aspecial purpose computer), special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

These computer program instructions may also be stored in a computerreadable memory or storage medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer readablememory produce an article of manufacture including instruction meanswhich implement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide steps for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

-   It is to be understood that the functions/acts noted in the blocks    may occur out of the order noted in the operational illustrations.    For example, two blocks shown in succession may in fact be executed    substantially concurrently or the blocks may sometimes be executed    in the reverse order, depending upon the functionality/acts    involved. Although some of the diagrams include arrows on    communication paths to show a primary direction of communication, it    is to be understood that communication may occur in the opposite    direction to the depicted arrows.

Computer program code for carrying out operations of the conceptsdescribed herein may be written in an object oriented programminglanguage such as Java® or C++. However, the computer program code forcarrying out operations of the disclosure may also be written inconventional procedural programming languages, such as the “C”programming language. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer. In the latter scenario, theremote computer may be connected to the user's computer through a localarea network (LAN) or a wide area network (WAN), or the connection maybe made to an external computer (for example, through the Internet usingan Internet Service Provider).

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, all embodiments can be combined in any way and/orcombination, and the present specification, including the drawings,shall be construed to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

It will be appreciated by persons skilled in the art that the presentembodiments are not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope of thefollowing claims.

1. A method for use in a radio node in a wireless communication systemfor one of transmitting and receiving a phase-tracking reference signal,PT-RS, the method comprising: obtaining information about a position ina time domain of a scheduled first demodulation reference signal, DM-RS,in a slot; and one of transmitting and receiving the PT-RS within theslot, the position of the PT-RS depending on the position in the timedomain of the scheduled first DM-RS.
 2. The method of claim 1, whereinthe obtaining comprises one of receiving information about anddetermining the position in the time domain of the scheduled firstDM-RS.
 3. The method of claim 1, further comprising: obtaininginformation about a position of a first time symbol in a slot scheduledfor data transmission; and obtaining information about a position of alast time symbol in the slot scheduled for data transmission.
 4. Themethod of claim 1, further comprising: obtaining information indicatinga scheduled modulation and coding scheme, MCS; and transmitting thePT-RS with a time density based on the scheduled MCS.
 5. The method ofclaim 4, wherein the time density is one of 1, ½ and ¼.
 6. The method ofclaim 1, further comprising: mapping the PT-RS to resource elements,REs, in the slot based on one or more of a position of the scheduledfirst DM-RS, a scheduled MCS, a required time density, a position of thefirst time symbol scheduled for data transmission and a position of thelast time symbol scheduled for data transmission.
 7. The metho/d ofclaim 1, wherein the first DM-RS is scheduled in resource elements, REs,which span a plurality of subcarriers in frequency and at least one timesymbol of the slot in time, while the PT-RS is one of transmitted andreceived in REs which span at least one subcarrier in frequency andmultiple time symbols of the slot in time.
 8. The method of any of claim1, wherein a physical resource block, PRB, of the slot has 12subcarriers in the frequency domain and one of 12 and 14 time symbols inthe time domain.
 9. The method of claim 1, wherein the radio node is awireless device.
 10. The method of claim 1, wherein the radio node is anetwork node.
 11. A radio node in a wireless communication systemconfigured for one of transmitting and receiving a phasetracking-reference signal, PT-RS, the radio node comprising: processingcircuitry configured to: obtain information about a position in a timedomain of a scheduled first demodulation reference signal, DM-RS in aslot; and one of transmit and receive the PT-RS within the slot, theposition of the PT-RS depending on the position in the time domain ofthe scheduled first DM-RS.
 12. The radio node of claim 11, wherein theobtaining comprises one of receiving and determining information aboutthe position in the time domain of the scheduled first DM-RS.
 13. Theradio node of claim 11, wherein the processing circuitry is furtherconfigured to: obtain information about a position of a first timesymbol in a slot scheduled for data transmission; and obtain informationabout a position of a last time symbol in the slot scheduled for datatransmission.
 14. The radio node claim 11, wherein the processingcircuitry is further configured to: obtain information indicating ascheduled modulation and coding scheme, MCS; and transmit the PT-RS witha time density based on the scheduled MCS.
 15. The radio node of claim14, wherein the time density is one of 1, ½ and ¼.
 16. The radio node ofclaim 11, wherein the processing circuitry is further configured to: mapthe PT-RS to resource elements, REs, in the slot based on one or more ofa position of the scheduled first DM-RS, a scheduled MCS, a requiredtime-density, a position of the first time symbol scheduled for datatransmission and a position of the last time symbol scheduled for datatransmission.
 17. The radio node of any of claim 11, wherein the firstDM-RS is scheduled in resource elements, REs, which span a plurality ofsubcarriers in frequency and at least one time symbol of the slot intime, while the PT-RS is one of transmitted and received in REs whichspan at least one subcarrier in frequency and multiple time symbols ofthe slot in time.
 18. The radio node of claim 11, wherein a physicalresource block, PRB, of the slot has 12 subcarriers in the frequencydomain and one of 12 and 14 time symbols in the time domain.
 19. Theradio node of claim 11, wherein the radio node is a wireless device. 20.The radio node of claim 11, wherein the radio node is a network node.